#include <stdio.h>
#include <math.h>
float length(float xa,float ya,float xb,float yb)
{
	return sqrt(pow(fabs(xa-xb),2.0)+pow(fabs(ya-yb),2.0));
}
int main()
{
	float x1 = 0;
	float y1 = 0;
	float x2 = 0;
	float y2 = 0;
	float x3 = 0;
	float y3 = 0;
	float l1 = 0;
	float l2 = 0;
	float l3 = 0;
	float p = 0;
	
	
	scanf("%f %f %f %f %f %f",&x1,&y1,&x2,&y2,&x3,&y3);
	l1 = length(x1,y1,x2,y2);
	l2 = length(x2,y2,x3,y3);
	l3 = length(x3,y3,x1,y1);
	p = (l1+l2+l3)/2;
	printf("%.2f",sqrt(p*(p-l1)*(p-l2)*(p-l3)));
	
	return 0;
}
